Conventionally, so called a linear motion rolling guide unit has been widely used which includes a rail, a movable block moving in a longitudinal direction on the rail, and a plurality of balls (rolling body) which are provided between the rail and the movable block, are circulating (revolving) while rotating (spinning) themselves to move the movable block with a high accuracy. Specifically, the linear motion rolling guide unit has been used in a member for supporting a three-dimensional motion of a work table of a machine tool or a pendulum motion of a pendulum railcar, and further in a seismic isolation structure of a building. It should be noted that the linear motion rolling guide unit includes not only the above described unit consisting of a movable block and a rail but also a so called ball screw.
With such a wide spread of the linear motion rolling guide unit, there is an increasing demand for failure prevention of the linear motion rolling guide unit, and what is needed is a diagnostic method for an operating state thereof with a high accuracy.
Here, as a method for diagnosing an operating state of a conventional general machine system (e.g., a rotational roller bearing unit including a ball bearing) excluding the linear motion rolling guide unit, for example, as shown in Patent Document 1 below, there is provided a vibration detecting method for diagnosing the operating state by monitoring a vibration generation state in the machine system; an oil evaluating method for diagnosing the operating state by extracting lubricating oil used in the machine system and evaluating the quality thereof; an electrical resistance method for diagnosing the operating state by measuring an electrical resistance between the members driven by way of lubricating oil in the machine system or a temperature measuring method for diagnosing the operating state by measuring, using a thermocouple or the like, the temperature of a member driven by way of lubricating oil in the machine system.    Patent Document 1: Japanese Patent Laid-Open No. 2004-93357